Expiry day is the last trading day of an option contract. At the close, every open contract is settled and disappears. In India the main index options have a weekly expiry, so expiry day comes around every week for NIFTY on NSE and SENSEX on BSE, and monthly for other indices and for stock options. The exact weekdays have changed several times; check the current calendar on the exchanges or on the NIFTY expiry page.
Options on their final day are sometimes called zero-day options or "0DTE" (zero days to expiry). They behave very differently from options with a week or a month left, and understanding why is the key to trading, or deciding not to trade, on expiry day.
What happens at the close
Index options are cash settled. The exchange works out a final settlement price for the index, which for NSE indices is the official closing value, itself based on prices in the last part of the session up to 15:30. Every call with a strike below that value and every put with a strike above it is in the money and pays the difference in cash. Everything else expires worthless.
Example: NIFTY settles at 25,068. The 25,000 call settles at ₹68 per unit. The 25,100 call and the 25,000 put settle at zero, whatever they traded at an hour earlier. Stock options are different: in-the-money stock options lead to delivery of shares, explained in the physical settlement guide.
Theta: time value disappears by the hour
An option's price is intrinsic value (what it is worth if exercised now) plus time value (the chance it gains more before expiry). On expiry morning an at-the-money NIFTY option is almost all time value, and that time value has to reach zero by 15:30. Decay that normally takes days happens in hours. The theta guide explains why decay speeds up near expiry.
The ATM straddle (call plus put at the strike nearest the index) is the clearest way to watch this. Here is today's NIFTY straddle, one point a minute:
On an expiry day, watch the slope of the line through the session: on a quiet day it slides steadily lower, while a sudden move in NIFTY shows up as a sharp spike as one leg gains value faster than the other loses it. On other days of the week the same chart falls more slowly.
Gamma: small moves, huge percentage swings
Gamma measures how fast an option's delta (its sensitivity to the index) changes as the index moves. Near expiry, gamma of near-the-money options is very high. In plain terms: an option a little out of the money can go from almost worthless to clearly in the money with a move of a few dozen points.
Suppose at 13:30 NIFTY is at 24,980 and the 25,050 call costs ₹6. If NIFTY rallies to 25,110 by 15:30, that call settles at ₹60, ten times its price. If NIFTY stays where it is, the call goes to zero. Sellers face the mirror image: the ₹6 they collected can turn into a ₹54 loss per unit. This is why expiry day attracts option buyers looking for a jackpot and why sellers on expiry day watch every tick.
Large open interest at nearby strikes affects how dealers hedge, which can either calm the index or make moves faster. The gamma exposure view sums this up:
Read the sign and the strikes where exposure is concentrated. Large positive exposure near the price tends to go with calmer, range-bound trading; negative exposure tends to go with faster moves. This is a tendency, not a rule; the gamma exposure guide explains it fully.
Pinning and max pain
On some expiry days the index seems to stick near a strike with very large open interest in the final hours. This is called pinning. One explanation is hedging: traders who are long many options at that strike buy dips and sell rallies to hedge, which pulls the price back. Another popular idea is max pain, the strike at which option buyers as a group would lose the most. The evidence for both is mixed; treat them as background, not as a forecast. The max pain guide covers the calculation and its limits.
Margins and rules on expiry day
SEBI and the exchanges have added measures aimed at expiry-day risk, including an extra margin on short options on expiry day and changes to how calendar spreads are margined on that day. Brokers often add their own limits, such as blocking far out-of-the-money option buying or selling after a set time. The details change, so check the current rules with your broker and on NSE before you trade on expiry day.
How a typical expiry day unfolds
No two expiry days are the same, but many follow a rough rhythm:
- 09:15 to 10:00. Premiums open with the time value left from the previous day plus any overnight gap. Spreads can be wider in the first minutes, and the straddle often makes its high of the day early.
- 10:00 to 13:30. If the index stays in a range, decay dominates and near-the-money premiums fall steadily. Sellers are usually comfortable here.
- 13:30 to 15:00. Little time value is left, so options trade closer to their intrinsic value. A move of even 50 to 100 points now changes which strikes end in the money, and cheap options can jump several times in minutes.
- 15:00 to 15:30. The settlement window approaches. Many positions are closed, liquidity in far strikes thins, and the last moves decide which options pay.
The same rhythm applies to MCX commodity options on their own expiry days, except that the evening session runs much later; check the exchange's timings.
How traders approach expiry day
- Sellers sell near-the-money straddles, strangles or iron condors in the morning to collect fast decay, usually with a stop-loss on the combined premium. Their risk is a sharp one-way move late in the day. See the intraday short straddle guide.
- Buyers buy cheap options expecting a breakout. Most such options expire worthless; the ones that pay off can pay many times over. Position size is the only real defence: risk only what you can afford to lose entirely.
- Hedgers close or roll positions before the last hour to avoid settlement surprises and wide late spreads.
- Observers use expiry day to learn: comparing the morning straddle with the actual move by the close shows whether options were overpriced or underpriced that day.
Common mistakes
- Buying far OTM options because they are cheap. A ₹2 option needs a large move just to survive; most expire at zero.
- Averaging down a losing option. On expiry day time is against the buyer every minute.
- Selling naked options without a stop. A late move of a hundred points can wipe out weeks of small gains.
- Waiting until the final minutes to exit. Spreads widen and prices jump; exit earlier if you do not want settlement.
- Trading size you would not trade on a normal day. Expiry day amplifies both gains and losses.